There are electronic musical instruments having automatic accompaniment function or automatic performance function and also having ad-lib performance function. The ad-lib performance function can be realized by procedures in which phrase data of a few bars is in advance assigned to each of keys in a specific range on a keyboard and built therein, and upon depressing each of keys in the specific range, phrase data assigned to the key concerned is read out from the beginning and allowed for note production only while depressing thereof.
The phrase data is built in as data of basic phrases according to C chord scale. In the automatic accompaniment function, when a chord by keyboard operation is detected, and in the automatic performance function, when a chord is detected in chord progression data inside song data, each of notes of a basic phrase are converted to notes on a chord scale note table corresponding to a detected chord and allowed for note production. The chord scale note table is constituted as a 12-scale note table starting from C root note according to each of chord types. Each of notes of the basic phrase is converted by adding a value according to root note of the detected chord.
Patent Literature 1 has described an electronic musical instrument having ad-lib performance function in which information on music sound waveforms of small-unit melody corresponding to each of keys in a specific range on a keyboard assigned for ad-lib performance is stored in advance, and, upon depressing each of keys in the specific range, music sound waveforms assigned to the key are read out to repeatedly reproduce musical sounds.
Patent Literature 2 has described an automatic accompaniment device in which an inverted form which can be naturally chained to a chord currently in note production is automatically selected, and note data is amended according to the inverted form, by which an interval will not jump before or after a change in chord in association with chord progression.